The legalese on the back of the tickets say: "Must be used by the same person on any and all days". So Amps, your parents could use them.
For the second part of your question, it gets a little trickier. It's one of those "depends on who you speak to" situations. They CAN seperate tickets from a package BEFORE your check in date, but it's a tedious process, and not well known amongst cast members. Further, you have to do it at Guest Relations - NOT the resort. So, my advice is to go to Guest Relations - no more than FIVE days prior to the check in date on your reservation. If the cast member you speak to says it can't be done, politely ask for a supervisor. If you're STILL told it can't be done, be ready to pay for tickets there.